As far as I know, only four companies held Traveller miniatures licenses prior to the recent MegaMinis/Ad Astra cycle.
Citadel, prior to the Warhammer days, and in partnership with RAFM, produced a 15mm line.
Martian Metals produced a separate 15mm line, but may have licensed the big grav tank.
Grenadier did a brief run of 25mm Traveller figs, consisting of four boxed sets (Imperial Marines, Civilians, Alien Mercenaries, and Alien Animals)
RAFM returned to Traveller during the TNE period with a 28mm line and a line of starships.
Finally, Hobby Products has a sadly short flirtation with 15mm SF that had several Traveller aliens make an appearance.
Of these lines, Grenadier, Martian Metals, and Hobby Products' lines have all vanished utterly. The RAFM 15mm line is around under generic trade dress, but without an explicit license the 28mm line and ships remain unavailable. The ships likely will stay that way unless and until Ad Astra ends their license.
MegaMinis produced 25mm aliens on an LE basis, and if they kept their sad promise, the masters and molds are gone. The ships they produced have since been sold to Ad Astra.